A high-energy-density, water- and heat-resistant supercapacitor based on a graphene/V₂O₅/MoS₂–La₂Ti₂O₇ composite electrode
L.A. Garcés-Patiño¹, H.J. Ojeda-Galván², A.C. Hernandez-Arteaga², J. Rodriguez-Gonzalez³, H.C. Rosu⁴, A.I. Mtz-Enriquez⁵, E. Ramos-Diaz⁶, J. Oliva¹
¹Centro de Física Aplicada y Tecnología Avanzada, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, Querétaro, 76230, Mexico. ²Coordinación para la Innovación y la Aplicación de la Ciencia y la Tecnología – UASLP, San Luis Potosí, S.L.P., 78210, Mexico. ³Cinvestav Unidad Monterrey, Parque de Investigación e Innovación Tecnológica, Apodaca, León, 66600, Mexico. ⁴División de Materiales Avanzados, Instituto Potosino de Investigación Científica y Tecnológica A.C., San Luis Potosí, S.L.P., 78216, Mexico. ⁵Cinvestav Unidad Saltillo, Parque Industrial Saltillo-Ramos Arizpe, Ramos Arizpe, Coahuila, 25900, Mexico. ⁶Academia de Ciencias, Universidad Politécnica de San Luis Potosí, San Luis Potosí, S.L.P., 78364, Mexico.
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Abstract
The V₂O₅/MoS₂–La₂Ti₂O₇ (VO/MLTO) composite was employed as a redox-active material to enhance the electrochemical performance of graphene-based supercapacitors (SCs), whose electrodes were fabricated by printing graphene (Gp) ink onto recycled polyethylene substrates. XRD analysis confirmed the formation of orthorhombic V₂O₅, hexagonal MoS₂, and monoclinic La₂Ti₂O₇ phases. Flexible SC devices were fabricated using VO (Gp+VO-SC), MLTO (Gp+MLTO-SC), and VO/MLTO (Gp+VO/MLTO-SC) powders as electrode materials. The Gp+VO-SC and Gp+MLTO-SC devices exhibited specific capacitance and energy density values of 756.3 F g⁻¹/105.0 Wh kg⁻¹ and 711.6 F g⁻¹/98.8 Wh kg⁻¹, respectively. The Gp+VO/MLTO-SC device reached higher specific capacitance and energy density values of 1,117.9 F g⁻¹ and 155.3 Wh kg⁻¹, corresponding to increases of 47.8% and 57.1% compared to devices based solely on VO and MLTO, respectively. The superior electrochemical behavior of the Gp+VO/MLTO-SC device is attributed to the synergistic interaction between its components, leading to favorable morphology and efficient charge transport. A homogeneous particle distribution promotes electrolyte ion diffusion and interaction with redox-active species (V⁴⁺/V⁵⁺, Mo⁴⁺/Mo⁶⁺, S²⁻/S⁶⁺, and Ti³⁺/Ti⁴⁺), while oxygen vacancies provide additional active sites and graphene acts as a conductive pathway for charge transport. The device also showed good durability, retaining 80.2% of its specific capacitance after 5000 charge–discharge cycles. It was further evaluated underwater at different temperatures. Immersion in water at 40 °C and 60 °C led to increases in specific capacitance of 7.1% at 40 °C and 10.1% at 60 °C compared to operation of the device in air. Overall, these results indicate that the VO/MLTO composite is a promising candidate for SCs capable of operating at elevated temperatures under aqueous conditions, making it suitable for portable and wearable applications.
Keywords: Supercapacitor; Composite; Graphene